Seismic Damage Evaluation of Steel Frames with Dual LCF System Under Critical Consecutive Earthquakes

This study investigates the effect of the linked beam behavior on the seismic damage of regular/irregular steel structures with dual LCF under critical successive shocks. For this, 12 steel frames with 3,6, and 9 stories containing shear/flexural linked beams in both regular and irregular configurations were designed and analyzed under critical consecutive earthquakes. The Park-Ang damage index was calculated and compared for all structures under different conditions (regular/irregular,flexural/shear linked beams). The results show that the shear behavior of the linked beam is more effective in reducing the damage of irregular structures. So that percentage of damage increases for sensitive stories due to the second-shocks was over 40% in LCF frames with flexural linked beams. Furthermore, average increase in damage due to the flexural linked beams was observed to be more than 3.7 times in irregular structures. During calculations, it was found that the successive shocks can lead to an increase of over 40% in average damage in irregular structures with flexural linked beams, whereas this value for shear behavior was reported to be around 30%. Finally, mathematical equations are proposed to estimate the ratio of the maximum increased damage index due to seismic sequence phenomenon in irregular versus regular structures.